The present invention relates to the combination of a fuel injection pump and a conversion device which converts mechanical movement into fluid pressure, in an internal combustion engine.
More particularly, the present invention relates to the combination of a fuel injection pump which has a movable fuel amount determining element with a conversion device which converts mechanical movement of this fuel amount determining element into fluid pressure. Thus a fluid pressure may be obtained which corresponds to the position of the fuel amount determining element, and this may represent the load on the engine.
For controlling various mechanisms on a present-day internal combustion engine, it is useful to have a quantity available which represents the load on the engine in some way. For instance, such a quantity can be used for the control of an EGR valve. Now, in the case of a gasoline engine, wherein the speed regulator is the inlet throttle valve which controls the amount of intake mixture, engine power output or load is largely affected by the engine intake amount. Therefore, if the engine revolution rate and the opening of the inlet throttle valve are measured, the percentage of the load to full power capacity, or "engine load ratio," can be approximately determined.
It is also possible, in an engine having an inlet throttle valve as the speed regulator, to determine the engine load ratio from the inlet manifold vacuum. For example, in an engine equipped with an electronic fuel injection system, there are some arrangements in which the inlet manifold vacuum is measured, and the fuel injection amount is controlled as based thereon.
In the case of diesel engines, however, because they are constructed differently from gasoline engines, there are not many elements reflecting the load which are available in order to determine the engine load ratio. In order, therefore, to determine this engine load ratio it becomes necessary to measure the rate of fuel consumption directly. However, this measurement in itself is difficult, and requires relatively expensive equipment, and therefore is not suitable for application to use in ordinary motor vehicles.
Further, ways are known conventionally to determine the engine load ratio from the position of the accelerator pedal, or from the position of the fuel injection pump lever. This kind of method can be implemented easily, but errors in manufacture in the governing mechanism or in the accelerator pedal linkage affect the accuracy of sensing of these amounts. Therefore, high precision determination of these quantities is not possible in this way. Also, particularly with an ordinary fuel injection pump, the provision of a governing mechanism means that the fuel injection amount is not directly proportional to the position of the control lever, so that it is not possible to determine positively the engine load ratio from the position of the control lever alone.